Crush roll arrangement for a card web

ABSTRACT

The present invention concerns a crush roll arrangement for a card web with two co-operating working rolls 6 and 10 as used, e.g. for crushing of seed and shell particles contained in a thin card web. At least one of the two rolls 6 and 10 is designed as a hollow member, the cylindrical sleeve 19 of which is pressurized inside and thus deforming in radial direction. By this deformation, which is counteracted by a second roll, the crushing pressure is generated between the working rolls 6 and 10. The sleeve 19 can, among other solutions, be of varying thickness along the longitudinal direction of the roll in such a manner that its radial deformation can be adapted in longitudinal direction along the working rolls 6 and 10.

The present invention concerns a crush roll arrangement for a card webwith two co-operating working rolls, such as used in staple fibrespinning, particularly in processing natural fibres.

Crushing a very thin fiber web, such as is taken off e.g. from thedoffer cylinder of a card, is carried out in order to reduce impuritiesstill contained in the web by crushing them, particularly the harderseed and shell particles crushing is accomplished in such a manner thatthe detrimental effect of the crushed impurities in subsequentprocessing operations is less disturbing and that the elimination of theimpurities from the fiber material is effected more easily.

In order to achieve good results using a crush roll arrangement of theabove type, the uniformity of the crushing pressure generated over thewhole working width of the rolls, which is of the order of 1 m, is ofdecisive importance. If the pressure is too low, the impurities are notcrushed or are not crushed sufficiently, i.e. the crush roll arrangementdoes not achieve the desired effect, whereas excessive pressures causedamage to the fibre material. Many efforts thus have been made toachieve a uniform loading of the crush rolls. These have resulted in anumber of proposed solutions, which however, are still unsatisfactory.

Thus, e.g. from German DT-PS No. 177 241 a crush roll arrangement forpaper, textiles, wood, leather and similar materials, is known, inwhich, for achieving better smoothness, the axes of the cylindricalcrush rolls are arranged at an angle with respect to each other. In acrossed arrangement of this type, a uniform pressure distribution can beachieved over the whole working width of the rolls in spite of thelateral loading of the rolls at the bearing support members. This knowncrush roll arrangement, however, shows substantial disadvantages: Theuse of pendulum bearings is required, which for setting the pressure areto be arranged adjustably. A design of this type, especially the crushroll drive mechanism, is complicated and expensive.

A further disadvantage is seen in that a certain crossing angle betweenthe crush rolls permits uniform pressure distribution only if a peciselydetermined load is applied to the bearing support members. If thebearing support members, e.g. are loaded excessively, the crush rollsare loaded at the edges, i.e. the pressure is higher toward the sideportions of the rolls than at the centre. In oder to vary the pressurebetween the rolls--a uniform distribution being maintained--the crossingangle must also the varied. This, however, is a tedious operation whichis difficult to control.

A further disadvantage of this known crush roll arrangement is thatrolls which are bent in their axes, are subject to a constantreciprocating load, which requires, among other inconveniences, acorresponding bending work.

According to another proposed solution (German DT-PS No. 904 150) auniform pressure distribution is to be effected using a crush rollarrangement with two working rolls which are supported over their lengthin such a manner that each working roll is supported by at least oneloaded support member, the support member being designed preferentiallyas a member of constant strength.

In a further development of this idea (German DT-PS No. 918 676) it hasbecome known to insert an elastic pressure transmitting member betweenthe working roll and the support member. The disadvantage of this crushroll arrangement is that, under the full pressure force, the rotatingcylindrical crush roll surface frictionally contacts the loaded supportmember or the pressure transmitting member, respectively. Thus,considerable energy losses and great danger of damage to the verysusceptible roll surface prevails.

Furthermore, from U.S. Pat. No. 3 457 618, magnetic crush rolls for cardwebs are known. Such crush rolls consists of a thin tubular steelsleeve, inside which a plurality of permanent magnets are uniformlydistributed over the whole width of the rolls, providing the magneticflux required. Such crush rolls permit establishment of a uniformpressure distribution. They show the disadvantage, however, that theirmanufacture is very expensive and that the pressure cannot be varied.

It thus is the object of the present invention to propose a crush rollarrangement which eliminates the disadvantages of the known arrangementsand in particular, permits achievement of a uniform and easilyadjustable pressure distribution over the whole width of the rolls.Furthermore, the arrangement is to be of simple design, economicallyfeasible and reliable.

These objectives are achieved with a crush roll arrangement for a cardweb with two co-operating working rolls, which are characterised in thatat least one of the two rolls is designed as a hollow member, thesubstantially cylindrical sleeve of which is under the influence of apressurized medium wetting the roll inside, and which is elasticallydeformable in a radial direction, and that the second roll is supportedat such distance as to counteract the deformation of the deformable rolllocally.

According to an alternative embodiment of the crush roll arrangement,the second roll also can be a hollow member which is elasticallydeformable radially toward the outside by a pressurized medium.

According to a further alternative embodiment, the roll inside availablefor the pressure medium is reduced by a rigid body. In this arrangementthe rigid body in a particular embodiment can be designed as a cylinderon the outside surface of which the roll sleeve is supported if themedium is in an unpressurized state.

The invention is described in more detail in the following withreference to the accompanying drawings wherein:

FIG. 1 schematically illustrates a side view of the web take-offelements of a card;

FIG. 2 schematically illustrates a longitudinal sectional view of acrushed roll arrangement in accordance with the invention;

FIG. 3a illustrates a view taken on line A--A of FIG. 2;

FIG. 3b illustrates a view similar to FIG. 3a of a pressurized roll inaccordance with the invention.

FIG. 4 illustrates an alternative embodiment of the crush rollarrangement in a longitudinal section;

FIGS. 5 through 9 illustrate further alternative design examples ofcrush rolls, the crush rolls being shown without bearing members andloading elements.

Referring to FIG. 1, a doffer cylinder 1 of a card transports on a pointclothing 2, a fiber web 3 (indicated with a dash-dotted line) from belowin the rotational direction indicated by arrow f₁ upward to a pointwhere the web 3 is deflected from the doffer cylinder 1 by a pointclothing 4 of a take-off roll 5 which rotates in the same direction(arrow f₂). The fiber web 3 contacts the substantially cylindricalsmooth surface of a lower working roll 6. A transfer roll 7, whichnormally is provided with a structured surface (in FIG. 1 four suitablydirected longitudinal grooves 8 are shown in the roll surface) ensuresthat the fiber web 3 is taken off the point clothing 4 and is depositedonto the surface of the lower working roll 6. Arrows F₃ and f₄ indicatethe rotational direction of the rolls 6 and 7, the length of the arrowsnot indicating any relation with the actual roll speeds. A rotatingbrush 9 is provided above the take-off roll 5 to insure the eliminationof any rest fibers from the point clothing 4 of the take-off roll 5.

The fiber web 3 is transported to the right, as viewed, by the lowerworking roll 6 and reaches a contact zone between the lower working roll6 and an upper working roll 10 which forms a crushing line with roll 6and rotates in the direction of arrow f₅. Here the web is subject to acrushing action known as such, in which the impurities contained in thefiber web 3, such as e.g. seed particles, sand particles, etc., arecrushed. The fiber web 3 upon leaving the crushing line is e.g.condensed by a funnel 11, and is taken off by two rolls 12 and 13 in theform of a fiber sliver 14 (see also FIG. 2) and is transferred to adepositing device (not shown).

The position of the working rolls 6 and 10 as shown in FIG. 1 can bechosen within the scope of the present invention also in a differentmanner; in particular, e.g. in such a manner that the axes of both rollsare located in one vertical plane.

As shown in FIG. 2, the lower working roll 6 is a solid roll, thesurface of which is substantially cylindrical, deviations from thisshape being entirely possible within the scope of the present invention,as explained later on. The lower working roll 6 is rotatably, but notmovably with respect to the room, supported in two anti-frictionbearings 17 and 18 mounted each in a side member 15 and 16 of the cardframe (not shown in more detail).

The upper working roll 10 consists of a substantially cylindrical, thinsleeve 19 which is tightly sealed at each end by a cover 20 and 21respectively, in such a manner that a pressure can be built up in theroll inside space 22. A suitable tight connection can be achieved, e.g.by welding (comp. FIG. 5 wherein the welding seam is designated 23).Also a tight press fit between the covers 20,21 and the sleeve 19, or asliding fit with a tight seal (both not shown), can be considered.

Each cover 20 and 21 respectively, extends towards the outside on anaxis 24 and 25 respectively, coaxial of the sleeve 19. The axes 24 and25 are rotatably supported in two support members 26 and 27 each with ananti-friction bearing 28 and 29, respectively. The support members 26and 27 in turn are slidably guided in the two frame side members 15 and16 respectively, as shown in FIG. 2 wherein fixing screws (not shown)which adjustably connect the support members and the frame side members,are indicated schematically with their axes m and n. For this purpose,the side member 15 contains a stop 30 for the support member 26, whichis pressed against the stop 30 by a pressure spring 32 arranged betweenan upper extension 31 of the side member 15 and the support member 26.The position of the stop 30 is chosen such that the whole force of thepressure spring 32 is taken up by the stop 30. A correspondingsymmetrical arrangement is provided at the left hand side. In this case,the pressure spring 32 has no influence on the area pressure between theworking rolls 6 and 10. This support arrangement provides a certainpossibility of yielding to the rolls in case any non-crushableimpurities are present in the fibre web 3 (FIG. 1), such as, e.g. ametal particle. In this case, the upper pressure roll 10 can be lifted,the pressure force of one or both pressure springs 32 being overcome, insuch a manner that the uncrushable impurity can pass between the workingrolls 6, 10 without damaging the roll surface, as would be the case withrigid support of both working rolls 6 and 10.

Furthermore it is noticed that bores are provided in the frame sideelements 15 and 16 for the axes 24 and 25 of the working roll 10, thediameter of which bores exceeds the diameter of the axes, in such amanner that they penetrate the side frames with sufficient clearance.

The left-hand side axis 25 of the roll 10 contains a coaxial bore 33which connects the roll inside space or interior 22 with a means forsupplying a pressurized medium to the interior of the roll 10. Thismeans includes a supply duct 35 which extends from a pump 34 by whichthe medium is pressurized. Between the rotating bore 33 and thestationary supply duct 35 a pressure-tight connection (not shown) isprovided. To the supply duct 35 furthermore a pressure measuring device36 is connected.

The pump 34 is supplied with the liquid 38 contained in reserve tank 37.Any compressible medium, however, e.g. a gas, can be used withoutdifficulty, as the only requirement of the medium is that it issufficiently pressurized. If a gaseous medium is used, a compressor canbe used instead of a pump 34. The reserve tank 37 in this case is notrequired anymore. The radial arrows f₆ indicated on the roll insidespace indicate the radial forces exerted by the medium onto the rollsleeve 19. Under the influence of these forces the sleeve 19 is deformedelastically over a distance r₁ -r₀ in such a manner that the sleevebulges outwards, as shown schematically in FIGS. 3a and 3b.

In its non-pressurized state the working roll 10 (FIG. 3a) the distanceM between the centers of the working rolls 6 and 10 equals the sum ofthe radii r₀ and R₀ of both rolls 6 and 10, i.e. in the non-pressurizedstate the upper working roll 10 contacts the lower working roll 6without load, or possible with a minimal load. The upper working roll 10thus is not deformed, i.e. the cross-section remains circular. In orderto achieve this, the axes of the rolls 6 and 10 with the correspondingsupport members can be supported in the most simple manner at fixedcenters at a distance M, which is differing from the arrangementaccording to FIG. 2. The area pressure between the working rollsaccording to the invention is generated by the deformation of theworking roll 10 caused by the pressure prevailing in the roll insidespace 22, as clearly indicated in FIG. 3b.

In FIG. 3b the increase of the diameter of the sleeve 19 of the upperworking roll 10 under the influence of the pressure is shown. But as thedistance M between the centers of the rolls 6 and 10 is maintainedconstant, the deformation of the roll 10 is locally impeded by the roll6, as roll 10 necessarily contacts roll 6. Thus the area pressurerequired for crushing the fiber web (FIG. 1) is generated.

The uniformity of the area pressure along the whole length of the nipline between the two working rolls 6 and 10 furthermore can be ensuredvery reliably in the manner described in the following:

By, e.g. suitably choosing the contour of the sleeve 19 of the upperroll 10 and/or of the lower roll 6, an equalisation of the deformationinfluence which varies over the width of the rolls can be effected. In aroll 10, which in a nonloaded state is cylindrical, the lower, solidroll 6 can be shaped correspondingly concave. Furthermore, the effectivewidth L (FIG. 2) of the pair of rolls, which corresponds to the width ofthe throughpassing web, can be chosen smaller than the total width ofthe rolls. Thus the influence of the radially not deformable roll endportions can be eliminated to a large extent.

The two working rolls 6 and 10 are connected by two gears 39 and 40 fordrive purposes. As the axes of the rolls 6 and 10 are maintainedparallel at all times and as the center distance M is maintainedconstant at all times, optimum conditions are ensured for the pair ofgears 39,40.

In FIG. 4 an alternative of the crush roll arrangement according to FIG.2 is shown, differing from the latter mainly in that both working rollsare designed as hollow members deformable in radial direction under theinfluence of a pressurized medium acting on the roll inside spaces.

In FIG. 4 an upper working roll 41 and a lower working roll 42 areprovided, designed in the same manner as the upper working roll 10according to FIG. 2. The diameters of the rolls 41 and 42 can bedifferent however. Also in this arrangement of the crush rolls, theeffective roll width L is smaller than the total width of the rolls 41and 42, in which a manner that the influence of the roll end portions onthe pressure distribution over the nip line is eliminated to a largeextent. Furthermore, the pressure prevailing in each roll differs. Forthis purpose, the upper working roll 41 is pressurized by means of afirst pump 43 via a supply duct 44. By a second pump 46 and via a supplyduct 47 on the other hand, the lower working roll 42 is pressurized andthus is deformed. The pressures applied are controlled by the twopressure masuring instruments 45 and 48.

Both pumps 43 and 46 are supplied with a liquid contained in a commonreserve tank 49. The pumps 43 and 46, however, also can be supplied fromseparate reserve tanks with the same liquid or with different liquids.

In FIG. 4 also the possibility is shown of influencing the function ofone of the working rolls by increasing or by lowering the temperature ofthe medium. This arrangement can prove advantageous in specialapplications of crush rolls, if e.g. the impurities can be renderedbrittle or less sticky by lowering their temperature. For this purpose,the lower working roll 42 is provided with a back-flow duct 50connecting the roll inside space with the reserve tank 49. The liquidsupplied by the pump 46 thus can flow through the roll 42. The liquid isheated, or chilled respectively, by a heat exchanger 51 provided in thecirculation circuit e.g. in the reserve tank.

In FIGS. 5 through 9 further alternative design examples of workingrolls are shown which can be applied within the scope of the presentinvention. As in all these examples the pairs of rolls are supported inthe same manner as described with reference to the examples shown inFIGS. 2 and 4, the further description can be limited to the actualdesign of the rolls.

In FIG. 5 a working roll 52 is shown, in which the roll inside spaceavailable for the pressure medium is reduced by spherical rigid bodies53 arranged in the roll inside space. Any other shape desired of thebodies also can be considered, from powdery material to one solidcylindrical body filling the space partially or wholly. By reducing theroom available for the pressure medium, a reduction of the total volumeof the medium required is achieved. Considering the fact that any mediumis of a certain compressability, this arrangement proves advantageous,as it ensures better constancy of the pressure maintained inside theroll.

The working roll 53 shown in FIG. 6 also consists, as all designexamples according to the invention, of a sleeve 54 deformable in radialdirection, which at both face surfaces 55 and 56, is welded to acylindrical body 57. Between the sleeve 54 and the cylindrical body 57an annular gap or space 58 extends over almost the full width of thesleeve 54, into which gap 58, the supply duct 59 for the pressure mediummerges.

In FIG. 7 a further alternative design example is shown of the workingrolls according to FIG. 6, in which a sleeve 61 in the non-pressurizedstate of the medium contacts the outside surface of a cylindrical body60, the diameter of which corresponds to the sleeve inside diameter. InFIG. 7 the upper half of the roll is shown in a non-pressurized state,whereas the lower half of the roll (below the centre line x) is shown ina pressurized state.

As different from the roll according to FIG. 6 no annular gap prevailsbetween the face sides 62 and 63, but the cylindrical body 60 fills thewhole roll inside determined by the sleeve 61 in the non-pressurizedstate. This alternative design example presents the advantage that thesleeve 61 in the non-pressurized state is supported and thus is alignedby the very massive, precise cylindrical body 60.

A plurality of connecting ducts 65 connect the central medium supplybore 66 with a cylindrical periphery of the cylindrical body 60. In thismanner, the distribution of the pressure medium throughout a gap 64between the sleeve 61 and the cylindrical body 60 is favoured. The sameeffect can be achieved by structuring the surface of the cylindricalbody 60, e.g. by grooves.

In this design example, furthermore, the application of an outsidepressure source is eliminated. The pressure inside the roll simply isestablished by providing an adjustable pressure piston 67 whichdisplaces the medium in the roll inside. The piston 67 guided in a bore68 of a hub 69 and provided with a suitable seal (not shown) if needed,is pressed against the liquid, filling the roll inside space by means ofa set screw 70 which is screwed into a corresponding threaded nut 71 ofthe hub 69. The advantage of this design example is seen in the utmostdesign simplicity. The use of particularly pressure resistant mediums,of course, is required in this example, such that the pressure and thusalso the deformation of the sleeve 61 is maintained constant over time.

The uniformity of the area pressure between the two working rolls can beachieved also in a different manner, namely in that the face covers 73and 74 (FIG. 8) are centrally connected mutually by a shaft 76 formingtwo hubs 77 and 78 as bearing positions for the working rolls outsidethe face covers. As shown, a sleeve 72 is welded to two covers 73, 74via welding seams 75 and an inside space is formed between the sleeves72 and covers 73, 74 which is subdivided into individual chambers 81 byringshaped intermediate walls 79 and 80. In this arrangement theintermediate walls 79 and 80 are designed in such a manner that they canyield to a radial deformation of the sleeve 72, whereas they arepressure-tight at the face side. Suitably chosen, concentrically,annularly ondulated sheet metal plates, e.g. can fulfill theserequirements.

Using suitable supply ducts, the individual chambers 81, 82 and 83 canbe pressurized. A pump 84 via a supply duct 85 pressurizes the chambers81 and 83 at the pressure p₁, whereas the chamber 82 is pressurized by asecond pump via a supply duct 87 at the pressure p₂. The pressure p₁ andp₂ respectively, can be checked by two pressure measuring instruments 88and 89 respectively. By suitably choosing the pressures p₁ and p₂, theshape of the sleeve surface in a loaded state (indicated by the brokenline t) can be influenced. Normally the pressure p₁ will be chosengreater than the pressure p₂, as indicated in FIG. 8, by the differentlength of the arrows indicating the pressure.

In FIG. 9 the equalisation of the area pressure is achieved by choosingvarying sleeve thicknesses over the roll width. In the upper half ofFIG. 9, e.g. the sleeve 90 of the roll is varied in steps towards themiddle, whereas in the lower half, the sleeve thickness graduallyincreases and decreases.

By such variations in thickness, which in FIG. 9 are shown exaggeratedfor better clarity, the resistance to deformation of the sleeve 90 canbe influenced along the width of the roll, in such a manner that in turnthe shape of the sleeve in a loaded state can be adpated to therequirements as desired. Thus, e.g. the dash-dotted line r indicates theoutline of a sleeve 90 of constant thickness. The broken line s, on theother hand, indicates the deformation of a sleeve 90, the thickness ofwhich is varied in steps over the roll width.

Furthermore, the various measures proposed for equalisation of the areapressure between the working rolls of a crush roll arrangement can becombined for achieving optimum results. Thus, e.g. a working roll can beprovided with a sleeve of varying thickness and can be subdivided inindividual chambers.

The most important advantages of the crush roll arrangement are:

(a) Parallel instead of crossed arrangement of the working rolls, suchthat any card can be equipped with a crush roll arrangement, withoutcomplicated bearing problems to be overcome, and that the area pressurebetween the working rolls can be adapted in a simple manner, the workingrolls being maintained parallel.

(b) Simple and economically feasible design, ensuring highly reliablecrushing action.

(c) Easy retrofitting on existing cards, as no particular requirementsare imposed for the bearing arrangement.

(d) Good influenciability and optimum uniformity of the area pressurealong the width of the roll.

(e) Easy change from operation with fiber web crushing action tooperation without such action. For this purpose it is sufficient torelease the pressure inside the working roll. This advantage is ofutmost importance is practical operation, as with each change in thematerial to be processed the question of suitability is to be re-checkedanew.

I claim:
 1. Crush roll arrangement for a card web with two cooperating working rolls characterised in that at least one of the two working rolls is designed as a hollow member, the substantially cylindrical sleeve of which is adapted to be under the influence of a pressurized medium on the roll inside and which is elastically deformable in radial direction, and that a second roll is supported at such distance to counteract the deformation of the deformable roll locally.
 2. Crush roll arrangement according to claim 1, characterised in that the second roll also is a hollow member, which is elastically deformable in radial direction towards the outside.
 3. Crush roll arrangement according to claim 1, characterised in that the inside space available for the pressure medium is reduced by a rigid body arranged therein.
 4. Crush roll arrangement according to claim 3, characterised in that the rigid body is a cylinder.
 5. Crush roll arrangement according to claim 4, characterised in that the sleeve in the non-pressured state of the medium contacts the outside surface of the cylinder.
 6. Crush roll arrangement according to claim 1, characterised in that the medium is a liquid.
 7. Crush roll arrangement according to claim 1, characterised in that the medium is a gas.
 8. Crush roll arrangement according to claim 1, characterised in that the inside space is connected via a pressure duct with an external pressure source arranged outside the roll.
 9. Crush roll arrangement according to claim 1, characterised in that the inside space is provided with an adjustable pressure piston displacing the medium.
 10. Crush roll arrangement according to claim 6 or 9, characterised in that the liquid is as incompressible as possible.
 11. Crush roll arrangement according to claim 1, characterised in that a heat exchanger for the medium is provided.
 12. Crush roll arrangement according to claim 1, characterised in that the roll inside space is sub-divided in individual chambers, at least one of which chambers is filled with pressure medium.
 13. Crush roll arrangement according to claim 1, characterised in that a plurality of adjacent chambers filled at different medium pressures are provided.
 14. Crush roll arrangement according to claim 1, characterised in that the sleeve in longitudinal direction is of varying thickness.
 15. Crush roll arrangement according to claim 1, characterised in that the working rolls are pressed against each other at their end positions by means of force accumulators.
 16. Crush roll arrangement according to claim 15, characterised in that both force accumulators each act against a fixed stop which takes up the full pressure force of the force accumulator.
 17. Crush roll arrangement according to claim 1, characterised in that the axes of the working rolls are arranged at fixed centres mutually.
 18. A crush roll arrangement for a card web comprising a pair of rolls for crushing impurities in a web passing therebetween, said rolls being rotatably mounted on respective longitudinal axes disposed at a fixed distance from each other during operation of the arrangement, at least one of said rolls having an outer radially deformable cylindrical sleeve and a space within said sleeve to receive a pressurized medium for radial deformation of said sleeve to increase the diameter of said sleeve whereby said sleeve deforms against the other of said rolls to define an area of pressure therebetween.
 19. A crush roll arrangement as set forth in claim 18 wherein said one roll includes a cylindrical body within said sleeve and said space is an annular gap between said sleeve and said body.
 20. A crush roll arrangement for a card web comprising a pair of rolls for crushing impurities in a web passing therebetween, said rolls being rotatably mounted on respective longitudinal axis disposed at a fixed distance from each other during operation of the arrangement, at least one of said rolls having an outer radially deformable cylindrical sleeve, a cylindrical body supporting said sleeve on a periphery of said body and a plurality of ducts in said body communicating with said periphery of said body for introducing a pressurized medium between said body and said sleeve for radial deformation of said sleeve to increase the diameter of said sleeve whereby said sleeve deforms against the other of said rolls to define an area of pressure therebetween.
 21. A crush roll arrangement for a card web comprisinga pair of rolls for crushing impurities in a web passing therebetween, said rolls being rotatably mounted on respective longitudinal axis disposed at a fixed distance from each other during operation of the arrangement, at least one of said rolls being an outer radially deformable cylindrical sleeve; and means for supplying a pressurized medium to said one roll to radially deform said sleeve whereby said sleeve increases in diameter and deforms against the other of said rolls to define an area of pressure therebetween.
 22. A crush roll arrangement as set forth in claim 18 or 20 or 21 wherein said other roll is hollow and elastically deformable in an outward radial direction.
 23. A crush roll arrangement as set forth in claim 18 or 20 or 21 wherein said one roll has a rigid body within said space to reduce the space for the pressurized medium.
 24. A crush roll arrangement as set forth in claim 18, or 20 or 21 wherein said one roll has an adjustable pressure piston therein for displacing the pressurized medium from said space.
 25. A crush roll arrangement as set forth in claim 18 or 20 or 21 which further comprises a heat exchanger for heating the pressurized medium in said one roll.
 26. A crush roll arrangement as set forth in claim 18 or 20 or 21 wherein said space in said one roll is sub-divided into individual chambers with at least one chamber filled with the pressurized medium.
 27. A crush roll arrangement as set forth in claim 18 or 20 or 21 wherein said sleeve is of varying thickness in the longitudinal direction thereof.
 28. A crush roll arrangement as set forth in claim 18 or 20 or 21 which further comprises force accumulators at each end of said rolls for pressing said rolls against each other. 